Roof support pillars support the roof of a vehicle and are located between the windows and doors of a vehicle. Roof support pillars are frequently identified as A, B, C, and in some instances, D-pillars depending on the vehicle style. A B-pillar is generally located immediately behind the front door of a vehicle, and extends from a floor pan and rocker panel upward to a vehicle roof. The B-pillar is an element in determining roof strength and the degree of side impact intrusion. The B-pillar may also be subjected to loads exerted on the doors in a vehicle side impact scenario.
Passenger vehicle designs are tested for roof strength and side impact strength. Conventional B-pillars are fabricated as multiple stamped sheet metal parts that are generally spot welded together. It is possible to improve the strength of conventional B-pillars by forming the sheet metal parts from high grade material, such as dual phase and boron steels. B-pillars may also be made stronger by using thicker gauge sheet metal components. However, the use of high strength alloys and thicker sheet metal may increase the weight of a vehicle and also increase the cost to manufacture the B-pillar. Even with the use of thicker alloy components, B-pillars of conventional design may not always meet stringent test requirements for roof strength and side impact performance.
Although stamped members have been used in vehicle body structures for many years, hydroformed components or members may be used in vehicles. Hydroforming is a cost-effective way of shaping malleable metals into lightweight, structurally stiff and strong pieces. Non-limiting examples of non-malleable metals includes aluminum or steel. One of the largest applications of hydroforming is the automotive industry, which makes use of complex shapes possible by hydroforming to produce stronger, lighter and more rigid unibody structures for vehicles. This technique is also popular with the high-end sports car industry, and is also frequently used to shape aluminum tubes for bicycle frames.
Hydroforming allows complex shapes to be formed, which would be difficult to manufacture with standard solid die stamping. Furthermore, hydroformed parts can often be made with a higher stiffness to weight ratio and at a lower per unit cost than traditional stamped or stamped and welded parts.
Referring now to the drawings wherein like reference numerals are used to identify identical components in the various views, FIGS. 1 and 2 show a prior art hydroformed body structure 100 where the C-Pillar 114 is integral to a roof side rail 118 and the A-pillar 123. Accordingly, with the use of the hydroforming process, the A-pillar 123, the roof side rail 118, and the C-Pillar 114 are formed from a single member. Moreover, the traditional structure includes at least one stamped cross member 130 at the roof structure 112 of the vehicle (not shown).
The traditional hydroformed body structure design 100 of FIGS. 1 and 2 anchor the roof rail 118 at the C-Pillar 114 given that the C-Pillar 114, the roof rail 118 and the A-pillar 123 are formed from a single member through the hydroforming process. The B-pillar 116 is typically a stamped member 117 and deforms prior to C-pillar 114 when the vehicle (not shown) experiences significant loads at the roof structure 112 as shown in FIG. 3.